The last item in the signal chain of the audio path of a push-pull type guitar amplifier is the output transformer. The signal runs through the output transformer before exiting the speaker. This transformer is a large blocky metal device mounted on the chassis of a guitar amplifier. This transformer converts the low current (and high voltage) signal to a low-voltage (and high current) signal that powers the speakers. The output transformer literally transforms, or transfers, the audio power of the amplifier onto a load (impedance) of the speaker; how efficiently it does this is one measure of quality and the modernity of technology and materials used. The speaker is thus driven, and literally transforms the signal from electrical into vibrational-mechanical signals through the air. Learn More